Page 902 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

operation, design, and management. The concept is based on the
theory that the complexities of a traditional network with on-device

configuration (i.e., routers and switches) often force an organization to
stick with a single device vendor, such as Cisco, and limit the flexibility
of the network to adapt to changing physical and business conditions.
SDN aims at separating the infrastructure layer (i.e., hardware and
hardware-based settings) from the control layer (i.e., network services
of data transmission management). Furthermore, this also removes
the traditional networking concepts of IP addressing, subnets, routing,

and the like from needing to be programmed into or be deciphered by
hosted applications.

SDN offers a new network design that is directly programmable from a
central location, is flexible, is vendor neutral, and is open standards
based. Using SDN frees an organization from having to purchase
devices from a single vendor. It instead allows organizations to mix
and match hardware as needed, such as to select the most cost-

effective or highest throughput–rated devices regardless of vendor.
The configuration and management of hardware are then controlled
through a centralized management interface. In addition, the settings
applied to the hardware can be changed and adjusted dynamically as
needed.

Another way of thinking about SDN is that it is effectively network

virtualization. It allows data transmission paths, communication
decision trees, and flow control to be virtualized in the SDN control
layer rather than being handled on the hardware on a per-device basis.

Another interesting development arising out of the concept of
virtualized networks is that of a virtual SAN (storage area network). A
SAN is a network technology that combines multiple individual
storage devices into a single consolidated network-accessible storage

container. A virtual SAN or a software-defined shared storage system
is a virtual re-creation of a SAN on top of a virtualized network or an
SDN.